The present invention relates to a reciprocating compressor. More particularly, the invention relates to an oscillation-type reciprocating compressor with oscillating piston in cylinder, that is easy to assemble and can maintain long-term durability even under high-pressure compression condition.
The reciprocating compressors have been used in various fields because they have a simpler structure than other gas compressors and are capable of high-pressure compression.
The reciprocating compressor includes a type (piston type) wherein a piston and a connecting rod are rotatably interconnected by a bearing mechanism as shown in FIG. 7 of JP-A No. 2008-297924, and an oscillation type wherein a piston rod and an upper compressing portion of a piston are formed in one piece as disclosed in JP-A No. 2006-152960.
The reciprocating compressor features a compact simple mechanism that can provide high-pressure compression and is now seeing an increasing user demand for higher performance and compression to higher pressure.
By the way, the oscillation-type reciprocating compressor disclosed in JP-A No. 2006-152960 has an advantage of being easy to assemble and reduced in manufacture costs because of the structure wherein a piston ring is mounted to the upper part of the piston. However, this compressor has a problem that the rotating piston is displaced out of axial alignment with a cylinder when the piston forms a large oscillation angle to the cylinder (see FIG. 6 of JP-A No. 2006-152960).
The piston ring is designed to accommodate such displacement. In the case of high-pressure compression, however, the piston rubs against an inside wall of the cylinder, worsening the problem of piston ring and cylinder scuffing.
As compared with the reciprocating compressor having the piston structure as shown in FIG. 7 of JP-A No. 2008-297924, such an oscillation-type reciprocating compressor has disadvantages of the simple structure of the compressing portion of the piston, a small proportion of metal portion and aptitude to heat propagation to a large end portion (rotary shaft).
In contrast to the piston-type compressor, the oscillation-type reciprocating compressor does not have a rider ring. During compression operation, therefore, the piston ring receives a greater lateral pressure than in the piston-type compressor and thence, is prone to failure or deformation.
During the compression operation, the oscillation-type reciprocating compressor may be decreased in performance due to seal failure of an abutment-joint portion of the piston ring. The seal failure may occur when the abutment-joint portion of the rotating piston ring is aligned in an oscillation direction.
The above-described problems are particularly serious at a high-pressure compression side of a multi-stage compressor.
The present invention is directed to solution to the above problems and has an object to provide an oscillation-type reciprocating compressor that can maintain high performance and long-term durability even under high-pressure compression condition and can prevent heat propagation to the large end portion.